The incidence of cervical and anal cancers in AIDS patients has remained substantial despite the introduction of potent antiretroviral therapy. Because these malignancies and their precursors are caused by human papillomavirus (HPV), the best hope for treatment in AIDS patients lies with the development of anti-HPV drugs. The HPV E2 protein is a logical target for drug development because it is critical for papillomavirus replication. In addition, it activates transcription of the viral E6/E7 oncogenes that cause cellular proliferation. However, E2 also prevents uncontrolled E6/E7 expression, making the loss of E2 function a critical step for HPV-associated carcinogenesis and raising serious concern over the wisdom of developing anti-E2 drugs. There also are in vitro studies indicating that E2 overexpression may be therapeutic. The most definitive assessment of a target for therapeutic intervention is through animal studies. While the actions of the E2 protein are being intensively studied in vitro, little work is being done in mammalian hosts. The proposed research aims to determine the effects of modulating, by conditional transgenesis, E2 activity in an animal model of papillomavirus-induced disease. Because the only papillomavirus genome that induces papillomas and carcinomas in experimental settings is the cottontail rabbit papillomavirus (CRPV), the CRPV-rabbit model will be used. The specific aims are to create vectors containing a full-length CRPV genome and a tetracycline-regulated E2 transgene. Vectors containing an E2 dominant-negative transgene will be used to determine the effects of E2 inactivation on papilloma growth, histopathology, CRPV DNA copy number, E6/E7 transcription, cellular proliferation and apoptosis. Vectors containing a conditional wild-type CRPV E2 transgene will be used to determine the effects of E2 overexpression.